Heat exchanger tubes



ICHIZO TAKAGI HEAT EXCHANGER TUBES Aug. 17, 1965 2 Sheets-Sheet 1 FiledMay 29, 1963 INVENTOR lav/20 72/04 1 Aug. 17, 1965 ICHIZO TAKAGI3,200,848 HEAT EXCHANGER TUBES Filed May 29, 1963 2 Sheets-Sheet 2INVENTOR [04/20 74mm BY 3,299,848 HEAT EXHANGER TUBES Ichizo Takagi, 56Nishi Kashiwahara @hinden, Yoshiwara-shi, dhizuolra, Japan Fiied May 29,1%.), Ser. No. 284,6ld6 1 Claim. (Cl. 138-38) The present inventiongenerally relates to improved heat-exchanger tubes, and morespecifically to heat-exchanger tubes in which improved type of fins areprovided.

Heretofore, various types of metallic heat-exchanger tubes have beenproposed, and among them there are the types of metallic heat-exchangertubes in which fins are secured to the outer periphery or innerperiphery of the tubes at right angles or in parallel with respect tothe axis thereof. Thus, the fins are initially formed separately fromthe tubes and then secured to the tubes. Another type of known metallicheat-exchanger tube is provided with the fins formed integrallytherewith as defined by projections on the tube wall.

The separate-outer-fin-type heat-exchanger tube is produced by theprocess which comprises the steps of disposing a plurality of finsaround the outer periphery of said tube, and expanding the tube diameterby any suitable means so as to tightly fit the inner peripheral surfacesof the fins on the outer peripheral surface of the tube. However,according to the process, since the tube is to be expanded, the materialfor the metallic tube should be formed by a soft metal. And therefore,the manufacture of such a type of heat-exchanger tube is rathercomplicated and in addition, this type of heatexchanger has inherentdisadvantages in that the fins often fail to be firmly secured atpredetermined proper positions on the outer peripherial surface of thetube and they tend to be dislocated from the anchoring positions whilein use of the heat-exchanger tube, and as a result good heatconductivity will not be provided by such a type of heat-exchanger tube.

The integral fin-type-heat-eXchanger tube is advantageous over theseparate fin-type-heat-exchanger tube in that the integralfin-type-heat-exchanger tube provides a better heat conductivity thanthe separate fin-type-heatexchanger tube and the integrally formed finswill not be dislocated in any way while in use. However, the integralfin-type also has to be formed from a soft metal and the productionefficiency of such a heat-exchanger tube is quite low as in the case ofthe separate fin-typeheat-eXchanger tube.

An object of the present invention is to provide improved metallicheat-exchanger tubes which eliminate the above-mentioned disadvantagesattendant upon the prior art metallic heat-exchanger tubes, and whichhave a broader heating surface, better heat conductivity, and simplerconstruction as compared with any of the prior art heat-exchanger tubes.

The novel metallic heat-exchanger tube according to the presentinvention is characterized in that said heatexchanger tube comprises ametallic tube, a corrugated metallic plate of copper or the like metalof round contour having good heat conductivity disposed within saidmetallic tube and having a plurality of alternately different-sized andalternately directed bends extending in the longitudinal directionthereof, and a plurality of cupshape anchor means press-fitted withinsaid bent metallic plate to firmly hold said metallic plate within saidtube, the edges of the inwardly directed bends of said bent metallicplate abutting against the outer peripheral surfaces of said anchormeans, the edges of the outwardly directed bends of said metallic plateabutting against the inner peripheral surface of said metallic tube, andthe sides common to adjacent inwardly and outwardfidilhdd Faterited Aug-9 W65 1y directed bends radially extending with respect to the aXis ofthe metallic tube.

The other objects, features and advantages of the present invention willbecome apparent to those skilled in the art from a reading of thefollowing detailed description of two preferred embodiments of thepresent invention.

In the accompanying drawings:

FIG. 1 is a cross sectional view of a preferred embodiment ofheat-exchanger tube constructed in accordance with the presentinvention;

PEG. 2 is a longitudinal sectional view of the embodiment of FIG. 1;

FIG. 3 is a front elevation view of the portion of a tin suitable to beused in the heat-exchanger tube according to the present invention andwhich illustrates the fin in its extended state prior to theinstallation thereof into the tube;

Phil. 4 is a cross sectional view of a modified embodiment ofheat-exchanger tube according to the present invention; and

FIG. 5 is a longitudinal sectional view of the modified embodiment asshown in FIG. 4.

Preferring now to the accompanying drawings, and especially to FIGS. 1and 2 in which the first embodiment of heat-exchanger tube by thepresent invention is shown, the novel heat-exchanger tube comprises ametallic tube 1 of such as a copper tube, which tube has an outerdiameter of 41.6 mm. and a wall thickness of 0.8 mm. and a corrugatedmetallic fin 2 curved to provide a round contour disposed within saidtube, which may be formed from a sheet metal such as copper or the likemetal having good heat conductivity and has a thickness of 0.5 min. Thecorrugated sheet metal 2 has been bent so as to have a plurality ofalternately different-sized and alternately different-directed bends asillustrated in FIG. 1. The heat-exchanger tube has also hemispherecupshape anchor means 33, which are formed of stainless steel and havean outer diameter of 18 mm. and a height of 12 mm.

In the formation of the above-mentioned novel hea exchanger tube, themetallic plate 2 as shown in FIG. 3 (which may be described as acorrugated plate in which the corrugations have flat tops and flatbases), is first deformed into a round shape or contour relative to itslongitudinal direction so as to provide a plurality of uniformly sizedand differently directed bends. The edges of the inwardly directed bendshave a width of 6 mm. and the edges of the outwardly directed bends havealso a width of 6 mm. The pitch of a pair of inwardly and outwardlydirected bends and the height of each bend is 11 mm. respectively. Thusdeformed, metallic plate 2 is then inserted into the metallic tube 1.After the insertion of said corrugated bent metallic plate 2 into themetallic tube ll, several hemispherical cupshape anchor means 3 (FIG. 2)are press-fitted with their curved surfaces 3a disposed at the sidewithin the bent metallic plate 2 by the use of any suitable means. Thus,the sides c common to adjacent inwardly and out- Wardly directed bendsare radially disposed with respect to the axis of the metallic tube l asshown in FIG. 1. On the other hand, the edges [1 of the outward bendsabut against the inner peripheral surface of the metallic tube 1 whilethe edges b of the inward bends abut against the outer peripheralsurfaces 3!) of the cup-shape anchor means 3 whereby the metallic plate2 which constitutes the fin can be firmly held within the metallic tube1.

Next, referring to FIGS. 4 and 5 which illustrate a modified embodimentof heat-exchanger tube according to the present invention, in thisembodiment the metallic tube 1 and cup-shape anchor means 3 are formedby the same materials as those employed in the first embodiment andtheir dimensions are also the same as those of the corresponding partsin said first embodiment. Therefore, the corresponding parts are giventhe same numerals as those in FIGS. 1 and 2 with alpha added thereto.However, the width of the edges b of the inward bends are selected as5.5 mm. shorter by 0.5 mm., than that or the edges of the outward bendsa which have a width of 6 mm. whereby a clearance 4 through which fluidcan pass may be formed between adjacent edges b of the inward bends.

Thus, according to the present invention, there are provided improvedheat-exchanger tubes having a much broader heating surface as comparedwith any of the known heat-exchanger tubes. By the mere insertion of thecup-shape anchor means into the interior of the metallic plate whichconstitutes the fin, the metallic plate or fin can be firmly held withinthe metallic tube. The production of the novel heat-exchanger tubes isquite simple when compared with the afore-mentioned prior artheat-exchanger tubes. Furthermore, since the fluid flowing within thetube is caused to impinge against the cup-shape anchor means and toproduce a turbulent flow, the heat-exchange efficiency of theheat-exchanger tube may be further improved, and especially, since themetallic tube may be equally formed from either soft or hard metal, thepresent invention has provided practical heatexchanger tubes whichpossess many advantages over the prior art heat-exchanger tubes.

It will be understood that minor modifications and changes may be madeon the foregoing embodiments by those skilled in the art withoutdeparting from the scope and spirit of the present invention.Accordingly, the invention is not to be limited to the preciseembodiments illustrated therein, but only by the scope of the appendedclaim.

What claimed is:

A heat exchanger tube comprising an outer metallic tube a corrugatedmetal sheet formed of a metal'having good conductivity,'the corrugationsof said plate having flat tops and fiat bases and the distance b tweenthe tops and bases of said corrugations being less than the radius ofsaid outer metal tube,

said corrugated metal sheet being curved to form a tube of roundconfiguration and being fitted within said outer tube with the flat topsof the corrugations thereof in contact with the inner surface of saidouter tube,

the width of the flat tops of said tube being sufiiciently greater thanthe widthof the fiat bases thereof to provide spaces between adjacentfiat bases when said corrugated metal sheet is curved to fit within saidouter tube, and

a plurality of spaced cup-shaped anchor means press fitted within saidcurved corrugated sheet with the flat bases of said corrugationsabutting against the outer peripheral surface of said cup-shaped anchormeans.

References Cited by the Examiner UNITED STATES PATENTS LEWIS J. LENNY,Primary Examiner.

EDWARD V. BENHAM, Examiner.

